<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">

<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>弹出层效果</title>
    <style>
    html,
    body {
        height: 100%;
        overflow: hidden;
    }
    
    body,
    div,
    h2 {
        margin: 0;
        padding: 0;
    }
    
    body {
        font: 12px/1.5 Tahoma;
    }
    
    center {
        padding-top: 10px;
    }
    
    button {
        cursor: pointer;
    }
    
    #overlay {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: #000;
        opacity: 0.5;
        filter: alpha(opacity=50);
        display: none;
    }
    
    #win {
        position: absolute;
        top: 50%;
        left: 50%;
        width: 400px;
        height: 200px;
        background: #fff;
        border: 4px solid #f90;
        margin: -102px 0 0 -202px;
        display: none;
    }
    
    h2 {
        font-size: 12px;
        text-align: right;
        background: #FC0;
        border-bottom: 3px solid #f90;
        padding: 5px;
    }
    
    h2 span {
        color: #f90;
        cursor: pointer;
        background: #fff;
        border: 1px solid #f90;
        padding: 0 2px;
    }
    </style>
    <script>
    window.onload = function() {
        var oWin = document.getElementById("win");
        var oLay = document.getElementById("overlay");
        var oBtn = document.getElementsByTagName("button")[0];
        var oClose = document.getElementById("close");
        oBtn.onclick = function() {
            oLay.style.display = "block";
            oWin.style.display = "block"
        };
        oClose.onclick = function() {
            oLay.style.display = "none";
            oWin.style.display = "none"
        }
    };
    </script>
</head>

<body>
    <div id="overlay"></div>
    <div id="win">
        <h2><span id="close">×</span></h2></div>
    <center>
        <button>弹出层</button>
    </center>
</body>

</html>
